The present invention relates to a ceramic heater for use in an intake pipe heater of internal combustion engines or the like purposes and, more particularly, to a novel construction of a flexible ceramic heater which is adaptable to external force and less liable to be broken.
Recently, there is a tendency that ceramic heaters having positive temperature coefficient (PTC) characteristics are used for mixed air-fuel gas heating devices of internal combustion engines.
The ceramic heater is formed mainly of barium titanate by baking, and exhibits a low electric resistance at normal temperature but the electric resistance is drastically increased at a so-called Curie point which usually falls between 120.degree. and 150.degree. C. In general, this ceramic heater is shaped to have a form of a thin disc and is pressed at its one side with a metallic plate as a heating medium or adhered to the same by means of a conductive adhesive during the use. Usually, the metallic plate constitutes a part of the casing of the ceramic heater. In the ceramic heater of the type described above, the casing is often distorted by a pressure exerted on the outside of the casing. The ceramic heater itself, however, is very fragile and can be distorted only slightly. In consequence, the ceramic heater is broken by such an external force or, even if it is not broken, a small gap is undesirably formed between the ceramic heater and the casing to deteriorate the heat transfer characteristics.
This problem would be overcome if the ceramic heater itself has a certain flexibility. This, however, is extremely difficult to realize.